The present disclosure relates, generally, to a wire mesh cable tray system and, in particular, to a component for a wire mesh cable tray that can be installed in the field to maintain equipment ground conductor (EGC) compliance for the wire mesh cable tray system.
Generally, a cable tray system is a rigid structural support system used to securely and mechanically support cables and wires across open spans. One type of cable tray is a wire mesh cable tray. Typically, these wire mesh cable trays are used at a job site for field adaptable support systems for a variety of cables such as, for example, low voltage, telecommunication and fiber-optics cables supporting analog and digital signals. In addition, the cables may be for applications that require different operational electrical voltages. The wire mesh cable trays are installed on short support spans between about four to about eight feet. These systems are typically steel wire mesh and zinc plated. Wire mesh cable trays have standard widths of 2, 4, 6, 8, 12, 16, 18, 20 and 24 inches, standard depths of 1, 2 and 4 inches, and a standard length of about 118 inches.
The manufacturing standard requirements for wire mesh cable trays are govern by the National Electrical Manufacturers Association (NEMA) and tested by establishments such as Underwriters Laboratories (UL) and the Canadian Standards Association (CSA). Additionally, installation procedures and practices are governed by a variety of codes, such as, for example, National Electrical Code (NEC). An UL classification indicates that the UL has tested the product and found its use suitable as an equipment-grounding conductor (EGC) and found that the product is intended for assembly in the field and for use in accordance with NFPA-70, National Electrical Code. In addition, the NFPA-70, National Electrical Code section 392.7 states a metallic cable system comprised of either steel or aluminum which is to be used as an EGC should be installed as per Table 392.7(b). In order to comply with Table 392.7(b) and to be certified as EGC compliant, the wire mesh trays need to 1) meet minimum cross-sectional area requirements as designated under Table 392.7(b); 2) not exceed a net resistance; and 3) be joined by mechanical connection.
A problem arises out in the field when the wire mesh cable tray systems need to be modified to adjust to the environment into which they are going to be installed. Such modifications can be bends and elevation offsets. The field installation technician may cut sections of the wire mesh cable trays out, bend, or form, the wire mesh cable tray into the desired configuration. For example, if a large radius bend in the wire mesh cable tray system is needed, the field installation technician would remove the wire mesh from alternate cross-sectional sections of the wire mesh tray along the longitudinal axis. The technician would then bend the ends of the wire mesh cable tray inward to form the radius of the bend as illustrated in FIG. 1. The technician can then secure the remaining cross-sectional sections of the wire mesh cable tray with connectors, such as, for example, expanding splice connectors and/or tee bolt assemblies, to maintain the new configuration. However, by cutting, bending or modifying the sections of the wire mesh cable trays, the cross-sectional area of the wire mesh cable trays can change. These environmental modifications can result in the wire mesh cable tray system no longer adhering to or complying with the EGC standards to which it had been manufactured.
Therefore, there is a need for components, either field-installed or manufactured, to be used with the wire mesh cable tray systems that maintain the cross-sectional area of the wire mesh cable tray as well as maintain the conductivity during bend and elevation offset modification to wire mesh cable tray system as required for the wire mesh cable tray system to comply with EGC standards.